The present invention relates to devices for holding samples and, more particularly, to contact plates with lids for enclosing samples, such as microorganisms.
A variety of sampling devices have been developed over the years for holding an agar media, or the like, in order to test whether microorganisms are present in a sample. One problem encountered with existing sampling devices is that the person who is using the device may have difficulty handling the sampling device and the sample without introducing contaminants that might affect the test.
Another difficulty associated with conventional sampling devices is that it often becomes hard to remove a lid from a dish because of a moisture seal lock. However, the opposite problem, the lid being inadvertently detached or removed when it is desired to maintain the sampling device in a covered state, may also be encountered with known sampling devices, which may adversely affect the ability to maintain, handle and/or store the sampling devices.
U.S. Pat. No. 5,854,065 describes one known type of microorganism sampling device. A base member is provided with a continuous sidewall providing a holding area for the agar media. A peripheral support surface extends around the base member at the external diameter of the base member outside the continuous sidewall. The lid member of the sampling device has a flange extending around the external diameter thereof, which includes a plurality of lugs downwardly extending therefrom that contact the peripheral support surface of the base member when the lid member is attached and define a gap allowing for airflow between the lid and base member to inhibit the creation of a moisture seal lock.
The count-tact Plate(trademark) from bioMerieux, Inc. of France is a further type of microorganism sampling device. The count-tact Plate(trademark) includes a base member with a continuous sidewall providing a holding area. The base member sidewall includes a plurality of ribs extending from an outer surface thereof that are contacted by the lid of the count-tact Plate(trademark) when the lid is pressed onto the base member by a user. The ribs may, thus, operate to removably connect the lid to the base member.
According to embodiments of the present invention, contact plates are provided including a base member and a lid. The base member has an upwardly extending sidewall extending circumferentially around a peripheral edge portion thereof to define a sample receiving area. The lid has a sidewall extending circumferentially around a peripheral edge portion thereof. A plurality of ribs extend inwardly from an inner surface of the sidewall of the lid. The ribs are configured to provide an interference fit engagement between the sidewall of the base member and the sidewall of the lid when the lid is attached to the base member.
In further embodiments of the present invention, the base member includes a contact surface extending around the sidewall of the base member outside the sample receiving area. The lid includes a flange member extending outwardly from a bottom end of the sidewall of the lid and positioned to engage the contact surface of the base member when the lid is attached to the base member. The contact surface of the base member may also include a plurality of ribs extending upwardly therefrom and positioned to engage the flange member of the lid when the lid is attached to the base member. The ribs of the base member and the ribs of the lid may together define an airflow passage to the sample receiving area when the lid is attached to and secured to the base member.
In other embodiments of the present invention, the ribs of the lid are configured to provide a retention force of between about 50 grams and about 2000 grams when the lid is attached to the base member and the flange member engages the contact surface of the base member. The ribs of the lid may be configured to provide a retention force of at least about 50 grams when the lid is attached to the base member and the flange member of the lid engages the contact surface of the base member independent of the rotational orientation of the lid relative to the base member on repeated attaching of the lid to the base member.
In further embodiments of the present invention, the ribs of the lid taper inwardly at a first angle relative to a central axis of the contact plate. An outer surface of the sidewall of the base member tapers inwardly at a second angle relative to the central axis of the contact plate. The first angle and the second angle are selected to provide the interference fit engagement. The first angle may be between about 3.5 degrees and about 4.5 degrees and the second angle may be between about 3.5 degrees and about 4.5 degrees.
In other embodiments of the present invention, the ribs of the lid have a height relative to the inner surface of the sidewall of the lid at a bottom side of the lid of between about 0.02 centimeters (cm) and about 0.04 cm. The ribs extending from an inner surface of the lid may have a width of between about 0.04 centimeters (cm) and about 0.09 cm. The inner surface of the lid may have a minimum radius about equal to a maximum radius of the outer surface of the sidewall of the base member. The inner surface of the lid may have a minimum radius within about 0.03 cm of a maximum radius of the outer surface of the sidewall of the base member.
In further embodiments of the present invention, the plurality of ribs extending from an inner surface of the lid includes at least 4 ribs. In some embodiments, 4 ribs may be provided positioned about 90xc2x0 apart around the inner surface of the lid. In other embodiments at least 12 ribs are provided. The at least 12 ribs may be positioned at substantially uniformly offset locations around the inner surface of the lid.